1. Field of Invention
The present invention relates to a dialysis machine comprising at least one filter for the filtration of the dialysis liquid and comprising means for determining the calcification of the dialysis machine. The invention further relates to a method of determining the calcification of a dialysis machine.
2. Description of the Prior Art
In the use of dialysis liquids which simultaneously contain high concentrations of calcium ions (Ca2+) and bicarbonate ions (HCO3−), the precipitation of lime (CaCO3) can occur and lime deposits can result in the dialysis machine as a consequence thereof. Under extreme conditions such as, for example, with an additionally low acid content, with long dialysis times or for the case that no decalcifying disinfection is carried out between two dialysis treatments, the said lime deposits can result in failure of the production of dialysis liquid, for example, by blocking of the conveying pumps or by calcification of dialysis liquid filters.
A dialysis machine is known from EP 0 834 328 A1 which comprises means via which an automatic decalcification of the dialysis liquid circuit of the machine can be initiated on the finding of a predetermined degree of calcification of the dialysis machine. Provision can be made in this process for the degree of calcification of the dialysis machine to be able to be determined by clouding of a window of a blood leak detector or by the determination of characteristic parameters of the conveying pump for the dialysis liquid. On the presence of criteria for a decalcification, provision can furthermore be made for the dialysis machine to initiate a decalcification cycle in a fully automatic process.
Whereas the problem of calcification at the machine side, which can result in an abortion of the dialysis and thus in a non-achievement of the treatment goal, is thus generally known, the effects of the lime deposition in the machine on the calcium supply to the patient have previously only been rarely looked at. It is evident that the calcium deposited in the dialysis machine, which is precipitated in the form of lime, can no longer reach the patient. It has been able to be shown in laboratory measurements that the precipitation of CaCO3 can lower the Ca2+ ion content at the dialysis-side inlet of the dialyzer to less than 50% of the prescription. This lowering takes place much faster than the failure of the machine due to calcification under specific conditions.
The case can thus occur that the patient is treated with a dialysis liquid for a fairly long time whose Ca2+-ion concentration is below the concentration of the ionized calcium in the plasma, which can have the consequence that calcium is removed from the patient in an unwanted manner in the dialysis treatment. The ionized Ca is of great significance with respect to nervous conduction, muscular contraction, myocardial contraction and blood pressure. It can therefore be imagined that negative effects on the patient can occur as a consequence of the machine calcification.